Attenuation of exercise-induced ST depression during combined isometric and dynamic exercise in coronary artery disease.
ST-segment depression was measured during submaximal dynamic (treadmill) and combined isometric-dynamic (isodynamic) exercise at comparable rate-pressure products in 11 patients (mean age 63 years) with stable coronary artery disease who were participating in an exercise training program. Each patient completed 3 separate trials. Trial 1 (baseline) was a submaximal treadmill exercise test to determine the threshold heart rate-systolic blood pressure (rate-pressure product) for ST-segment depression (greater than or equal to 1.0 mm). During trials 2 and 3, patients performed (in random order) dynamic treadmill exercise and isodynamic exercise (treadmill walking 1.5 to 2.0 mph carrying 15 to 25 kg) until threshold rate-pressure product was achieved. During trial 1, each patient showed significant ST depression (mean 1.7 mm) at target rate-pressure product (mean 18,200). Subsequent dynamic exercise trials 2 and 3 showed similar mean ST depression (1.5 mm) and rate-pressure product (18,000). During isodynamic exercise trials 2 and 3, subjects showed only minimal ST depression (mean 0.4 mm) at a rate-pressure product similar to dynamic exercise (mean 18,590). Heart rates were significantly lower (-10/min) and systolic (+20 mm Hg) and diastolic (+25 mm Hg) pressure was higher during isodynamic exercise (p less than 0.05). The rate-pressure product is not a valid index of ST response during isodynamic exercise in stable exercise-trained cardiac patients. Attenuation of ST depression during isodynamic exercise may be attributed to a combination of increased diastolic perfusion pressure, decreased heart rate and possibly to reductions in venous return and ventricular diastolic wall tension due to increased intrathoracic and abdominal pressure.
Bertagnoli
K
K
Cardiology Section, University of Wisconsin, Madison 53792.
Hanson
P
P
Ward
A
A
D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D003327:Coronary Disease / Q000175:diagnosis* / Q000534:rehabilitation; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged